1. Field of the Invention
The invention relates to a method for operating a system consisting of a plurality of internal combustion engines and a control device for carrying out the method.
2. Description of the Prior Art
From practice, systems consisting of a plurality of internal combustion engines are known, which are coupled in such a manner that drive outputs provided by the internal combustion engines are drawn by at least one common consumer. In sum total, the drive outputs provided by the internal combustion engines of the system in this case provide a total output drawn by the at least one or each common consumer.
From practice it is known, furthermore that either each internal combustion engine of such a system of internal combustion engines is assigned an individual exhaust gas aftertreatment device or multiple internal combustion engines of such a system of internal combustion engines are assigned a common exhaust gas aftertreatment device. In particular when an individual exhaust gas aftertreatment is arranged downstream of internal combustion engines, the exhaust gas of each respective internal combustion engine is subjected to an individual exhaust gas aftertreatment in the respective exhaust gas aftertreatment device. When a common exhaust gas aftertreatment device is arranged downstream of a plurality of internal combustion engines the exhaust gas of this plurality of internal combustion engines is combined for the common exhaust gas aftertreatment and then conducted via the common exhaust gas aftertreatment device.
Such an exhaust gas aftertreatment device can for example be an SCR catalytic converter, in which nitrogen oxides are converted into nitrogen and water vapour using a reduction agent such as ammonia. An NO oxidation catalytic converter can be connected upstream of such an SCR catalytic converter, to convert NO into NO2 upstream of the SCR catalytic converter and thereby increase the speed of reaction in the SCR catalytic converter. Additionally or alternatively, an exhaust gas aftertreatment device can also comprise a CH4 oxidation catalytic converter to reduce for example CH4 emissions, which are incurred in particular in the case of gas engines.
During operation there is the problem that exhaust gas aftertreatment devices are subjected to coking-up with hydrocarbons and/or with fuel-generated and engine oil-generated sulphates and sulphides in particular when operating temperatures of the exhaust gas aftertreatment devices are too low over an extended period of time, as a result of which the respective exhaust gas aftertreatment device is deactivated or loses its effectiveness. Such a deactivation is reversible and can be reversed by raising the exhaust gas temperature in terms of a regeneration of the respective exhaust gas aftertreatment device, as a result of which the respective exhaust gas aftertreatment device regains its original activity.
During the operation of a system consisting of a plurality of internal combustion engines, downstream of which individual exhaust gas aftertreatment devices are arranged, or downstream of which a common exhaust gas aftertreatment device is arranged, the regeneration of the respective exhaust gas aftertreatment device causes difficulties. The reason for this among others is that for effective regeneration of an exhaust gas aftertreatment device the drive output of at least one internal combustion engine of the system of a plurality of internal combustion engines has to be reduced. However this is not possible in particular when the internal combustion engines each provide drive outputs for at least one common consumer, since the drive power that is then available to the common consumer would be reduced and the same could no longer be fully operated.